Voltage regulator circuitry

1. A system comprising: first voltage regulator circuitry operable to supply a first regulated output voltage to a load; second voltage regulator circuitry operable to supply a second regulated output voltage to the load; and controller circuitry operative to selectively enable one of the first and second regulator circuitry and disable the other of the first and second regulator circuitry so as to supply either the first regulated output voltage or the second regulated output voltage to the load; wherein the second voltage regulator circuitry is selectively operable in either: an open-loop mode in which the second regulated output voltage is regulated based on a reference voltage; or a closed-loop mode in which the second regulated output voltage is regulated based on the reference voltage and a voltage indicative of the second regulated output voltage; and wherein the system is configured to control the operation of the first and second voltage regulator circuitry such that: the second voltage regulator circuitry is enabled for operation in its open loop mode prior to disabling the first voltage regulator circuitry such that the second voltage regulator circuitry is able to supply the second regulated output voltage to the load at a magnitude that is sufficient to meet a minimum supply voltage requirement of the load during a transient load spike that occurs immediately after the first voltage regulator circuitry has been disabled.

2. A system according to claim 1 wherein the system is configured to control the operation of the second voltage regulator circuitry such that: when the second voltage regulator circuitry is enabled, the second voltage regulator circuitry is operative in the open-loop mode for a first period of time; and after expiry of the first period of time, the second voltage regulator circuitry is operative in the closed-loop mode.

3. A system according to claim 1 wherein the system is configured to control the operation of the second voltage regulator circuitry such that: when the second voltage regulator circuitry is operative in the closed-loop mode a magnitude of the second regulated output voltage decreases over time.

4. A system according to claim 3 wherein the system is configured to control the operation of the second voltage regulator circuitry such that the magnitude of the second regulated output voltage decreases in one or more steps over time.

5. A system according to claim 1 wherein the first and second voltage regulator circuitry comprise low drop-out regulator circuitry.

6. A system according to claim 1 wherein the second voltage regulator circuitry has lower power consumption than the first voltage regulator circuitry.

7. A system according to claim 1 wherein the load comprises RAM.

8. A device comprising the system according to claim 1 , wherein the device comprises a mobile telephone, a tablet or laptop computer, a portable media player, a gaming device, a wearable device or an accessory device.